Look at the files. Then run "tex ppaper" or "latex lpaper".
This will create an auxiliary file with requests for bibliography
entries.

Run "bibtex ppaper" or "bibtex lpaper". This program will try to
satisfy the requests mentioned above by creating a "bbl" file.

Run "tex ppaper" or "latex lpaper" again. And again. Now look at the
output.

If you are going to use bibtex on a regular basis, start building
your own file "mybib.bib", and add references whenever you need them
for a new paper. Also, whenever you publish a paper, add its refernece
to mybib.bib.

More information:

Leslie Lamport,
"LaTeX : a document preparation system",
Addison-Wesley, 1986. -- This is the original source for BiBTeX.